Fixes related to QT5_GENTOO_CONFIG, QT_FEATURE_* macros, qconfig_p.h header

[Arfrever]

Fixes related to QT5_GENTOO_CONFIG, QT_FEATURE_* macros, qconfig_p.h header.

Problem was accidentally found during work on Qt 5.15.6 version bump (#260), but older versions are also affected.

In Qt 5.15.5:

$ grep -Er '(QT_CONFIG|QT_REQUIRE_CONFIG)\((dbus|dbus_linked)\)' *
src/gui/kernel/qguiapplication.cpp:#if QT_CONFIG(dbus)
src/gui/kernel/qguiapplication.cpp:#endif // QT_CONFIG(dbus)
src/platformsupport/services/genericunix/qgenericunixservices.cpp:#if QT_CONFIG(dbus)
src/platformsupport/services/genericunix/qgenericunixservices.cpp:#endif // QT_CONFIG(dbus)
src/platformsupport/services/genericunix/qgenericunixservices.cpp:#if QT_CONFIG(dbus)
src/platformsupport/services/genericunix/qgenericunixservices.cpp:#endif // QT_CONFIG(dbus)
src/platformsupport/services/genericunix/qgenericunixservices.cpp:#if QT_CONFIG(dbus)
src/platformsupport/services/genericunix/qgenericunixservices.cpp:#if QT_CONFIG(dbus)
src/platformsupport/services/genericunix/qgenericunixservices.cpp:#if QT_CONFIG(dbus)

Both src/gui and src/platformsupport are in QT5_TARGET_SUBDIRS in dev-qt/qtgui ebuilds. Previously some D-Bus-dependent code was disabled even for dev-qt/qtgui[dbus].

src/platformsupport/services/genericunix/qgenericunixservices.cpp:

#if QT_CONFIG(dbus)
// These QtCore includes are needed for xdg-desktop-portal support
#include <QtCore/private/qcore_unix_p.h>

#include <QtCore/QFileInfo>
#include <QtCore/QUrlQuery>

#include <QtDBus/QDBusConnection>
#include <QtDBus/QDBusMessage>
#include <QtDBus/QDBusPendingCall>
#include <QtDBus/QDBusPendingCallWatcher>
#include <QtDBus/QDBusPendingReply>
#include <QtDBus/QDBusUnixFileDescriptor>

#include <fcntl.h>

#endif // QT_CONFIG(dbus)
...

[a17r]

fwiw, rebasing 5.15.6 bump on top of this built fine, but I haven't tried 5.15.5.

Correction: Subsequently, dev-qt/qtdeclarative failed ot build, and revdeps too. https://gist.githubusercontent.com/a17r/0b15913b0823f9c7c0b6cc1d402c6d62/raw/3c840963ad062ce1b2582f5b1ed543b1487e04d0/dev-qt:qtdeclarative-5.15.6:20220917-151454.log Successful build for comparison: https://gist.githubusercontent.com/a17r/0b15913b0823f9c7c0b6cc1d402c6d62/raw/cf4d1e364f6834e4addd1f0092044c0699792881/dev-qt:qtdeclarative-5.15.6:20220917-154658.log